The present invention generally relates to apparatus and method of an integral gas turbine assembly. More specifically, the present invention relates to apparatus and methods relating to an assembly comprising an integral bell mouth, impeller shroud and diffuser.
Gas turbine engine aircraft may utilize an auxiliary power unit (APU) for a variety of tasks under a variety of conditions. An APU may include various modules, for example, a cooling module, a generator module, a compressor module, and a combustion module, that may each perform different functions.
During operation of a conventional APU, air may enter a compressor module where it may pass through a compressor wheel rotating between an impeller shroud and a housing. The air may then be accelerated by the compressor wheel outwards at an increased speed towards a diffuser. The diffuser, which may include a ring of static vanes, may then function to slow the accelerated air down for other uses.
Accordingly, a conventional compressor module may include multiple static components which create cavities, and assemblies that various rotational components of the compressor module may function in. Examples of conventional static components may include an air inlet, a bell mouth against which incoming air may impinge, an impeller shroud about which blades of a compressor wheel may rotate, and a diffuser.
When an aircraft is not in flight, an APU may operate in an open loop configuration, wherein a gas turbine may be fired to produce power required to operate various systems on the aircraft. When the aircraft is engaged in flight, the APU may transition to a closed-loop operational mode, which may utilize main propulsion engine bleed air for power. These two modes of operation may have different operational parameters, such as the operational temperature of the various components and the temperature of the incoming air. Differences in operational parameters between these two modes of operation may require different clearance controls between rotating groups and static structures for the APU to operate efficiently.
However, a conventional multiple component compressor module may include various separate components which may be arranged into various separate assemblies. As such, thermal and mechanical loading differences which may be brought about during transient conditions, may exist between the various separate components of a conventional compressor module. Such differences in the components may not allow for accurate prediction of structural behaviors of the various components of a conventional multiple component system during transient conditions that may include a transition from open loop operation to closed loop operation, or the reverse. Since accurate prediction of structural behaviors may be difficult if not impossible to predict, enhancing performance and durability of a conventional multiple component compressor module by controlling parameters that depend on such structural behaviors may be difficult.
For example, enhancing performance of an APU may be accomplished by more uniformly controlling a thermal response on a compressor shroud in combination with a diffuser. However, changes in thermal response as may be experienced during a transition from open loop operation, to a relatively hotter condition brought about by closed loop operation, may result in an inability to control such a thermal response in a multiple component compressor module. An inability to control such a thermal response may be due, in part, to a lack of thermal communication between a compressor shroud and a bell mouth. Partial control over thermal response may be obtained by adding additional components to the compressor module, such as, a grid over an inlet that may uniformly distribute airflow at the inlet. A conventional multiple component compressor module may also require a variety of fasteners, braces, and the like to maintain structural integrity of the module. However, such additional components may be undesirable because they may add weight, cost, and complexity to the system, thus may not provide for a robust system.
In addition, tighter clearances between various components of a conventional multiple component compressor module which may enhance performance of a compressor, may be prevented due to limitations in manufacturing methods, and/or by the cumulative build up of the tolerances among the various components of a conventional multiple component compressor module, and/or other modules and components. Furthermore, the multiple component approach of the prior art may create undesirable leak paths between various components arranged within a conventional multiple component compressor module.
As can be seen, there is a need for a compressor module assembly which may allow for a more accurate prediction of structural behaviors of the various components due to thermal and mechanical loading during transient conditions. There is also a need for a compressor module assembly which may be produced with existing manufacturing tolerance capabilities that may improve the efficiency of the compressor module by, for example, enhancing flow on a higher flow momentum from a compressor edge blade into a diffuser, while maintaining current manufacturing techniques. In addition, there is a need for a compressor module assembly which may prevent, or minimize, leak paths between various components. There is also a need for a compressor module assembly which does not require a plurality of fasteners and/or other support members that may add mass to the unit.